1. Field of the Invention
The present invention relates to processes of using an aperture data base system to prepare, inspect and display data for direct-writing by a charged particle ray, including a cell projection pattern; and an exposure system making these processes possible.
2. Related Art
In the process for producing a semiconductor integrated circuit device, there is made practicable a finely-working technique for rendering an integrated circuit pattern, using a focused beam of a charged particle ray, such as an electron beam or an ion beam. For example, in an electron beam exposure device, an electron beam is radiated onto a wafer to which an electron beam sensitive resist is applied, so as to expose the wafer directly to the beam scanned in the form of an integrated circuit pattern. Thus, the integrated circuit pattern is directly formed. In order to obtain a drawn pattern by the electron beam (EB), an EB mask is used (Japanese Patent Application Laid-Open No. Hei 6-5500). This EB mask has a rectangle aperture and a cell projection aperture. The rectangle aperture is used for focusing the electron beam into a rectangle form, together with rectangle apertures that other EB masks have, and radiating the beam in a rectangle pattern whose size is variously changed onto the wafer. The cell projection aperture is an aperture for a partial pattern resulting from taking out a part of a direct-writing pattern that should be radiated onto the wafer. The cell projection aperture is used for radiating the beam having this partial pattern in a lump on the wafer. A plurality of the cell projection apertures are made in the mask and they are selectively used on the basis of designed data.
In a process for controlling exposure to light in a conventional electron beam exposure device, a table 1 as shown in FIG. 1 is prepared. The table 1 shows a correlative relationship about data including cell names of cell projections, which show aperture patterns of cell projection apertures; aperture numbers, which show respective positions, in the mask, where the respective cell projections are formed; and dose ranks, which show radiated amounts. As shown in FIG. 2, an operator judges whether or not designed data include a cell projection pattern (step S1). In the case that the designed data include no cell projection pattern, the designed data are subjected to processings such as removal of overlapping and format-conversion (step S2) to prepare variable shaping data for using a variable shaping aperture. The data are output as EB data.
On the other hand, in the case that the designed data include a cell projection pattern, a cell about which the number of reference is large is searched on the basis of the cell structure of the designed data. The resultant cell is extracted and specified as a cell projection pattern (step S3). Layout data, mask-bias values, and the like are added to the extracted cell projection pattern to obtain data for preparing an aperture (step S4). In the case that the designed data are converted to the EB data, cell projection data such as cell names, mask aperture numbers and dose ranks are designated in the form of, e.g., a table by hand-input, so as to specify a cell projection pattern (step S5). On the basis of these cell projection data, a flag of cell projection is raised for the pattern. The address of the cell projection pattern is designated by hand-input (step S6). The cell projection pattern is outputted as data for direct-writing in a cell projection (EB data) (step S7).
However, the above-mentioned process for preparing EB data in the prior art has the following drawbacks. Parameters for direct-writing in a cell projection need to be artificially inputted, and the aperture data are not linked with the table supplied at the time of the data conversion. Therefore, at the time of processing the data conversion, artificial mistakes may be made. Besides, much time is required for the data conversion.
The outputted EB data per se need to have information on the shape of a cell projection pattern. Thus, there is a problem that a volume in the data increases.
It is an object of the present invention to provide a process for preparing data for direct-writing by a charged particle beam, a process for verifying data for direct-writing by a charged particle beam, a process for displaying data for direct-writing by a charged particle beam, and a light exposure device which make it possible to prevent input-mistakes, perform data conversion into EB data quickly, and reduce a volume in the EB data.
The process for preparing data for direct-writing by a charged particle beam according to the present invention comprises the steps of:
storing plural patterns of cell projections made in an aperture in a register, and comparing cells in designed data with the cell projections stored in the register by an interlayer operation,
judging whether or not a cell which coincides with any one of the cells in the designed data is present among the patterns of the cell projections stored in the register from the results of the interlayer operation,
extracting, in the case that the judgement that the coinciding cell is present is given in the judging step, the coinciding cell projection, and
outputting the extracted cell projection as data for direct-writing.
This process for preparing data for direct-writing by a charged particle beam preferably comprises, in the case that the judgement that no coinciding cell is present is given,
second judging, when referring the cells in the designed data to the cell projections stored in the register, whether or not a cell whose reference frequency is over a given value is present in the designed data,
second extracting, in the case that the cell whose reference frequency is over the given value is present in the designed data, this cell, and
registering this cell as a new cell projection.
After the extracting step and the second extracting step, this process preferably comprises the designating step of reading out cell projection pattern information, which include an aperture number and an aperture area, from the register, and designating the data.
This process preferably comprises the mask data outputting step of outputting data for preparing a mask having the pattern of the cell projection stored in the register.
The process for verifying data for direct-writing by a charged particle beam according to the present invention comprises the steps of:
storing plural patterns of cell projections made in an aperture in a register, and judging whether or not writing data include a cell projection pattern,
first format-inverting the writing data to obtain format data, in the case that the writing data include no cell projection pattern,
second format-inverting alternative data so as to obtain format data after outputting a call for obtaining cell projection information to the register so as to obtain cell projection pattern alternative data from the register, in the case that the writing data include the cell projection pattern,
comparing these format data resulting from the format-inversion with designed data by an interlayer operation.
The process for displaying data for direct-writing by a charged particle beam according to the present invention comprises the steps of:
storing plural patterns of cell projections made in an aperture in a register, and judging whether or not writing data include a cell projection pattern,
first displaying the writing data as a pattern layout, in the case that the writing data include no cell projection pattern,
second displaying an alternative data as a pattern layout by outputting a call for obtaining cell projection information to the register so as to obtain said alternative data of cell projection pattern from the register, in the case that the writing data include the cell projection pattern.
This process for displaying data for direct-writing by a charged particle beam preferably comprises inputting the call for obtaining the cell projection data so as to obtain a mask layout from the register, and displaying this mask layout.
The exposure device according to the present invention comprises a source for radiating a charged particle ray, a mask having a cell projection aperture, a unit for focusing the charged particle ray, a first deflector for deciding a position on the mask irradiated with the charged particle ray, a second deflector for deciding a position on a wafer irradiated with the charged particle ray, a controlling unit for controlling irradiation of the wafer with the charged particle ray and the cell projection aperture in connection with each other, and a register in which patterns of cell projections are stored. The controlling unit compares a cell projection of designed data with the cell projections in the register by an interlayer operation and then extracts, in the case that both of them coincide with each other, the coinciding cell projection from the register to use this coinciding cell projection, together with pattern information including an aperture position in the mask and an aperture area, as writing data.
In this exposure device, in the case that the cell projection of the designed data does not coincide with the cell projections stored in the register by the interlayer operation, the controlling unit extracts a cell projection about which the repetition reference frequency of the register is over a given number, and registers the cell projection newly into the register.